Document 1 (JP 2007-5847 A) discloses a network which includes a network relay device configured to connect a terminal to a shared device by way of a link. The network relay device judges whether or not transmission of data between nodes is allowed, on the basis of conditions concerning at least one of a source node and destination node of the data.
However, the network disclosed in document 1 cannot perform dynamic access control of prohibiting communication between nodes normally and of allowing the communication between the nodes if necessary.